I've been trying to implement the MS-20 filter from this paper http://lib.tkk.fi/Dipl/2010/urn100219.pdf
highlighted by Peter McCullough in a previous post about the MS-20 filter. Maybe someone has done it already I don't know. Aaaaanyhoooo my knowledge of these things is not great and I am stumped by the saturation part of the filter. Basically I've done something very wrong as the filter overloads pretty easy and resonance isn't in the correct place.
Anyone offering help will be thanked verily.